FI72289B - BUCKET SHEET FOR MACHINE HAIRDAD GIPS ELLER CEMENTERAND MAERIAL AND FOERFARANDE FOER DESS FRAMSTAELLNING - Google Patents

Description

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C (45) city / X ^ TWa '' '·' ·· - j *. , -, 4 · - * | i ^ -? · r. f · nj K .B 32 B 13/14, 13/02, 31/12, (51) Kv.lk. /Int.CI. E 0 ^ 4 C 2/26 FINLAND —FINLAND (21) Patent application - Patentansökning 801765 (22) Filing date - Ansöknlngsdag 30.05.80 (23) Starting date - Giltighetsdag 30.05.80 (41) Publication - Blivit offentlig 01 .12.80

National Board of Patents and Registration For publication and publication, date. - 30.01.87

Patents and registries' 1 Ansökan utlagd och utl.skriften publicerad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed - Begärd priority 30.05.79 England-England (GB) 7918871 (71) BPB Industries Limited, Ferguson House, 15 Marylebone Road, London,

England-England (GB) (72) Thomas Albert Pilgrim, Edwalton, Nottinghamshire, Eng 1 anti-Eng 1 and (GB) (7 * 0 Oy Kolster Ab (5 * 0 Building board comprising hardened gypsum or cementitious material and method of its The present invention relates to a building board comprising a core of hardened gypsum or cementitious material and a layer of inorganic fibrous layer on one or both surfaces of the core and a method for making the same.

Conventional paper-coated gypsum or gypsum boards are sufficiently strong and refractory for many purposes, but there are potential applications for such a board that require high strength and / or high refractory.

It has been proposed to increase the strength of cementitious building boards by reinforcing the curable cementitious material of the frame with fibrous materials, but this has only been partially successful. The complex processes involved in assembling a product laminated from fiberglass mats and gypsum boards to a mold, as described, for example, in British Patent 1,520,411, are not economical, and in the finished product, the fiber barrier extends throughout the product. In addition, the thick gypsum mixture does not saturate the carpet and the thin mixture, mainly water, passes through. The use of fibers dispersed in a cementitious material, such as glass fibers, presents difficulties in effectively disintegrating the fibers into the mixture, and insufficient bonding between the fibers and the surrounding cementitious material results in strength limitations.

Others have suggested making the product in exactly the same way as gypsum board, but using intervening mineral fibers instead of a conventional paper coating, as in British Patent 769,414. British Patent 772,581 discloses the fiberglass fabric passes through the mortar mixture before applying the blend layer and the second impregnated glass fabric. In either case, it is uncertain whether the curtain tissue is satisfactorily saturated and whether adequate binding has been achieved.

Canadian Patent 993,779 proposes the formation of a gypsum board by depositing a gypsum mortar mixture on a sheet of inorganic fibers on a conveyor and then applying another similar fiberboard and pressing one between the rollers so that the mixture penetrates the fiberboard surfaces. It has been found that this process results in only partial and irregular permeation and, as a result, leaves the surface of the board rough and both fibers and gypsum are visible on the surface.

U.S. Pat. In each case, the fabric and the alternative sheet resist the penetration of the gypsum and the structure is formed simply by successively superimposing different sheets and configurations on the forming table and conveyor. In each case, the product has the tissue surfaces defined by the outer plates and the plates themselves can only be imperfectly bound to the heart.

British Patent Specification 2,013,563 (published August 15, 1979) discloses the manufacture of gypsum board, a board having one surface coated with a conventional paperboard (paper) on which the mixture is run in a conventional manner while applying a glass fiber board over the core mixture and forcing the combs. This product has one side of paper and 3 72289 has only the properties of conventional gypsum board, while the other side is gypsum and is roughly unprotected against wear and other mechanical damage.

British Patent Specification 2,004,807 (published April 11, 1979) discloses a method of making a thin reinforced gypsum board, vibrating the board with a fiberglass fabric covered with dry mortar so that the mortar crystals penetrate the fabric and then spraying water as the vibration continues to mix the mortar and water. As the mortar hardens, a reinforced gypsum board is formed in which the fiber is distributed throughout the thickness of the board.

A new building board and process have now been developed that allow the disadvantages of the prior art to be avoided or overcome economically.

The building board according to the present invention is characterized in that the web-shaped fibrous layer is impregnated with the core material and that the core material also extends through the fibrous layer and forms a continuous film over the outer surface of the board.

The method of manufacturing a building board according to the present invention is characterized in that the web-shaped inorganic fibrous layer is contacted with one or both surfaces of the aqueous slurry layer of cementitious material between opposing support surfaces and that the support layer (s) over the outer surface of the continuous film layer.

The permeable fabric or fabric may take a variety of shapes, such as a perforated sheet or film of an inherently impermeable material, but it is highly fibrous and most preferably mineral fiber.

The core need not contain fiber, but it may contain small amounts of fiber to increase its cohesiveness. The contribution of the fibers to the strength of the board is greatest when the fibers are close to the surfaces of the board, so the increase in maximum strength obtained by using a given amount of fibers is realized by using a fabric or tissue embedded immediately adjacent to the core surface.

The reinforcing fibers are hot glass fibers and may be in the form of woven or knitted fabrics or nets, but are preferably in the form of a nonwoven fabric or fabric bonded with a suitable synthetic resin.

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Immersing the fibers in the surface of the core and forming a continuous film on them of cementitious material increases the fineness of the final surface of the board while ensuring that the fibers are concentrated in the most efficient location, as close to the surface of the board as possible.

The method of the present invention can be easily implemented in a continuous manner so that the sheet is continuously produced on a production line. The permeable fabric or fabric is glued to the lower support surface, then a core layer is applied, followed by another fabric or fabric, the assembled sheet structure is then moved under the second support surface, and the assembled sheet structure is moved forward between the support surfaces while vibrating the appropriate areas. The resulting sheet is allowed to cure and can be cut and dried in a conventional manner.

In addition, it has been found that a continuous film formed by a vibration-permeable mixture of fabric or tissue is usually condensed or densified and is harder and less porous than the core material of the sheet. This can be attributed to the increased pressure acting on the surface, the pressure which exists when the mixture passes through the fabric or tissue, which transition indicates a pressure gradient in this direction.

According to another aspect of the invention, the invention provides a building board comprising a core of cementitious material, such as gypsum, the core lined on at least one side with a permeable fabric or fabric embedded in the core surface and a continuous film of cured cementitious material having a higher density and porosity the density and porosity of the core material extending over the outer surface.

As previously mentioned, the fabric or fabric should be close to the surface and it is preferred that the thickness of the uppermost continuous film does not exceed 2 mm or even 1 mm, but may be as thin as possible provided that the mixture is sufficiently charged so that the finished the desired surface is obtained on the plate. The surface may be smooth or may have a random or patterned fabric, depending on the surface of the conveyor belt or other support. The compacted structure makes it possible to obtain a fine surface finish. The core can be of the desired thickness, for example the same thickness as the standard thickness values of the gypsum board.

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Popular fabrics and fabrics are fiberglass nonwoven fabrics. The fabric may be glued with a resin, for example a urea formaldehyde resin, as is usual when using fiberglass fabrics. The weight of such a fabric may be about 60-80 g / m 2, but this value is in no way critical and, for example, fibers with a diameter of 10-20 or 13-15 are suitable. The two such fabrics thus correspond to an amount of fibers of 120-160 g / m 2 of the board, which when the standard thickness of the board is 9 mm can be 1-2% of the weight of the board mortar. This relatively small proportion of fibers emphasizes the economics of the present invention in terms of the amount of fiber used, and the strength of the sheet can be adjusted by varying the strength of the fabrics used.

The fibers of the nonwoven fabric may be randomly applied or oriented. In the former case, the tensile strength of the plate is essentially the same in both the longitudinal (machine) and transverse directions. In the latter case, the plate may have high strength in the longitudinal direction but low strength in the transverse direction. In this respect, the board resembles a conventional gypsum board, although the average strength of the board may be substantially increased if 2 is desired. For example, a 60 g / m, substantially random, fabric applied to both surfaces provides the same strength in both directions, which is greater than the transverse strength of a conventional gypsum board but less than its longitudinal strength.

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The latter value is exceeded if an 80 g / m fabric is used. The longitudinal orientation of the fibers in a 60 g / m fabric increases the strength of the board in this direction, with a corresponding decrease in the transverse strength, and thus the strength properties of a conventional gypsum board can be approached. By changing the properties of the fabric, the strength of the sheet can be strengthened in a certain direction or additional strength can be reserved at certain points, for example along the edges of the sheet, by using a suitable fiber division in the fabric.

A woven glass fabric or a loosely woven reinforcing fabric may be used, but is more expensive and / or less effective than a nonwoven fabric.

The core mixture may contain a small amount of glass fiber, for example 0.3-3% by weight of the mortar, to increase cohesiveness, but may be as fibrous as conventional gypsum board.

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According to the invention, sheets made using a mineral fiber fabric or fabric do not require a paper coating of conventional gypsum board or the addition of starch to the core mixture. Thus, they may be of a completely non-combustible material and the drying step in their manufacture may be relatively rapid with its associated advantages, including low energy consumption.

The available fiberglass fabric and reinforcing fabric is usually porous enough to permeate the mixture sufficiently to vibrate to form the desired surface film. Permeation can also be aided by preheating the mixture or adding surfactants.

The fabric or fabric may be impregnated before being applied to the mixture with surface modifying additives, such as waterproofing and reinforcing agents, for example, synthetic resins. If the impregnated layer is not allowed to dry before application to the core mixture, the mixture will carry at least a portion of the additive in the layer as it passes through the layer, so the additive will modify the gypsum (or other cementitious) surface film as desired. Thus, for example, if the waterproofing agent is applied to a fabric or fabric, the waterproofing surface can be formed using a much smaller amount of additive than would be necessary to add to the core mixture in a conventional method.

The main belts between which the board is formed should be of a material that is not easily adhered to by the mortar mixture. Most of the plastic materials used for the belts are suitable for this purpose. The straps are brightly flexible to be able to transfer local vibration to the plate assembly after the fabric is applied to the core mixture.

Any suitable vibrator device can be used for vibration. At present, it is preferred to use horizontal rotating shafts, shafts with an angular cross section and mounted to rest against the rear surfaces of the belts. Instead of simple mechanical devices, other vibrating systems can be used, including ultrasonic systems.

A mineral fiber-coated gypsum board production technique according to the present invention will now be described by way of example 7 72289 with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a gypsum board manufacturing apparatus according to the invention and Figure 2 is a schematic sectional view (not to scale).

As can be seen in Figure 1, water 10, beta-hemihydrate gypsum plaster 11, together with conventional additives and about 3% staple fibers 12 of the desired length are passed to a mixer 13 in conventional proportions, the mixer comprising a gutter conveyor 14 and mixer devices 15 a mixture.

If the core contains small amounts of staple glass fibers or no fibers at all, the gutter mixer 13 does not need to be used, but can be replaced by a simple screw mixer or Ehrsam-type rotary plate mixer 13a which discharges the mixture to the fabric 21 through the glass gutter 13b.

The fiberglass web 17 is fed from the roll 18 and placed on the upper surface of the return portion of the upper support conveyor belt 19. The second glass fabric 21 is fed from the roll 22 onto the surface 23 of the lower support conveyor. The conveyor belts are suitably formed of polypropylene and provided with respective belt washers 24 and 25 and are operated in the direction of the arrows. The cross-sectional belts attached along the side edges of the lower belt 23 define the mixture and determine the width of the plate, as will be explained below.

The mortar mixture fed by the mixer 13 forms a dam 26 between the converging belts 19 and 23 and the fabric layers 21 and 25 at the inlet between the pair of support conveyors. At the inlet, the belts pass over and contact the respective vibrators 27. The vibrators may be in the form of, for example, square axes of rotation which rotate at a sufficient speed, for example about 1000 rpm. The vibration conducted from the vibrators 27 via the support belts causes the fabrics 21 and 24 to sink into the respective surfaces of the mixture and the mixture penetrates through the fabric and forms a continuous film on contact with both sides of the core and tissue composition.

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The combined material held between the belts 21 and 24 then passes under a roll 29 which gives it the desired thickness and when the sheet arrives at the end of the conveyor, the mortar is sufficiently hardened and the resulting sheet 29 is divided into lengths and transferred to a continuous dryer in a conventional manner.

The result is a gypsum board with a roughly conventional core 31 and smooth, minimal but high density, nonwoven surface layers 32 covering the nonwoven fabrics 33. The nonwoven reinforcement is centered on the surface and gives the board the maximum strength properties that can be achieved per unit area of the board. The hard, dense surface layers 32 give the surfaces of the sheet a good finish.

A typical example of a board prepared as described is a gypsum board with a nominal thickness of 9 mm and coated with a fabric made of glass fibers with a diameter of 13 μg glued with urea formaldehyde resin and weighing 60 g / m 2. When the core had 0.3% by weight of staple glass fibers (optional feature), the plate had a refractive index of 7.3 N / mm in both the longitudinal and transverse directions.

The plate made according to the present invention has a dense surface, the structure of which has been examined microscopically.

Scanning electron micrographs indicate that the surface layer of gypsum on the embedded glass fiber formed by the vibration-permeable mixture is dense and uniform and has only a small uniform outer film with a less dense area between this outer film and the glass fiber fabric. The heart, on the other hand, is more porous, while the gypsum immediately below the level of the tissue is also relatively porous and more reminiscent of the heart than the surface of the layer.

Examination of a particular plate prepared as described in the example, scanning electron micrographs and quantitative measurements show that the thickness of said surface layer on top of the glass fiber fabric was 0.17 mm and the thickness of a portion of said highly uniform outer film-forming layer was 0.03 mm. The density of the upper part 0.1 mm from the surface layer (thinner sampling was not possible) was 1.158 g / cm 2. The density of said outer film was even higher.

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The density of the 1.7 mm thick portion 3 immediately behind the glass fiber fabric was 1.096 g / cm; The density of the 1.9 mm thick portion of the central portion of the 3 hearts was 1.095 g / cm; the density of the 0.66 mm thick portion taken from the surface of the sheet, comprising the fibrous web and the outermost film, was 0.983 g / cm 3; the aforementioned 0.66 mm thick portion from which the outer film 3 was removed (i.e., a 0.63 mm thick portion) had a density of 0.946 g / cm) (i.e., the density of gypsum in the area of the glass fiber fabric is lower than in the surrounding core); the density of gypsum in the area of the glass fiber fabric (determined by dissolving the gypsum using 20% hydrochloric acid and correcting it with the effects of acid on the glass fiber) was 0.995 g / cm 3.

The above density values must be compared with the core density of a conventional gypsum board of 0.86 g / cm.

It should be noted that although there is variation in the density and porosity of the cured cementitious material from the outer surface of the slabs of the invention to the core, and although reference is made here to different layers and portions of the slab (e.g., surface layer or film, outer film, core), the slab is generally integral. the cured cementitious material (e.g., gypsum) forms a continuous and uniform matrix extending from one side through one or both of the permeable fabrics or fabrics to the other side. The term core is used herein not only for the central portion of a sheet, a sheet having a permeable fabric or fabric in both opposite major surface areas, but also for a corresponding portion of a sheet having a permeable fabric or fabric on only one of these surfaces.

As previously mentioned, a permeable fabric or fabric is preferably fiber, most preferably one that contains mineral fibers, of which glass fibers are generally the most important. However, the phenomenon in which a film of curable cementitious material is formed on the permeable fabric or fabric, which is denser and less porous than the core, can also occur quite advantageously when other forms of fabric or fabric permeable to the mixture are used. For example, the mixture may penetrate the perforated sheet and form a continuous sealed film, a sheet, which is initially a material impermeable to the mixture, for example a plastic sheet with multiple perforations.

For example, perlite and / or vermiculite and / or urea formaldehyde resin can also be added to the mixture used for the heart. Such an addition generally does not penetrate the permeable fabric or tissue.

The sheets according to the invention do not have to have the high strength values obtained in the above examples, although in general the strength values follow those obtained in the examples.

Claims (8)

1. A building board (29) comprising a core (31) of hardened plaster or cementing material and an inorganic fiber layer (17, 21) on one or both surfaces of the core, characterized in that a web-shaped fiber layer (17, 21) is impregnated with the material of the core (31) and the material of the core also extends through the fiber layer (17, 21) and forms a continuous film (32) over the outer surface of the disk (29). 2. A building board according to claim 1, characterized in that the material of the surface film (32) has a greater density and less porosity than the material of the core (31) itself. 3. A construction sheet according to claim 1 or 2, characterized in that the fibrous layer (17, 21) is a resin bonded fiberglass fabric. 4. A building board according to any one of claims 1 to 3, characterized in that the thickness of the continuous film (32) does not exceed 2 millimeters. 5. A building board according to any one of claims 1-4, characterized in that the continuous film (32) comprises an outer surface membrane, the density of which is greater and the porosity less than the density and porosity of the other film. Process for making a building board according to claim 1, characterized in that web-shaped inorganic fiber layers (17, 21) are contacted with one or both surfaces of a water slurry layer of cementing material (26) between opposing supporting surfaces (19, 23). and that the support surface (19, 23) (or the support surfaces) in contact with the fiber layer (17, 21) is subjected to vibration until the slurry penetrates the layer and forms a continuous film (32) over the outer surface of the layer (17, 21). 7. A method according to claim 6, characterized in that the support surfaces (19, 23) are flexible strips and that they are subjected to vibration by mechanical movement directed at the surfaces which are removed from the slurry.